A spot weld is a commonly used technique for holding two pieces of sheet metal or other material together. A spot weld is formed by placing two pieces of sheet metal in facing contact with each other and connecting the two sheets into an electric welding circuit. Two small diameter cylindrical electrodes are placed on opposite sides of the position to be welded. The two surfaces to be welded are compressed together by the electrodes as electrical current is passed between the electrodes to heat the spot weld area. The interface between the two metal sheets becomes heated sufficiently to weld the two sheets together at a small spot in the vicinity of the two electrodes.
A common application for spot welding is in automobiles where fender quarter panels or other body parts are secured to structural members. It is often necessary to remove these panels, such as when an automobile must be repaired following an accident.
In addition to removal of a panel for repair or replacement following an accident, it is often necessary to remove an undamaged panel from an automobile that is being salvaged. After removal the panel is then substituted for a panel that has been damaged.
Welded panels are typically removed by drilling out the spot weld with a drill bit that is roughly equal in diameter to the diameter of the spot weld region. In order to minimize damage to the parts involved, it is desirable to drill through one of the two fastened parts only to the depth of the facing surfaces between the two parts. In this way only one of the parts is damaged by the drill and the other remains substantially intact.
Where a damaged fender panel is being removed one would drill through the fender and preserve the body mounting. Alternatively, where a good fender is being removed for use on a different vehicle, it is desirable to drill through the body member and preserve the integrity of the fender panel.
However, metal is a difficult material to drill through and frequently the spot welds are positioned in inconvenient, hard to get at locations. It can thus be quit difficult to drill through the spot weld interface without drilling at least part way through the second panel. The problem becomes even worse when relatively unskilled labor is used to perform the drilling operation.
It is thus highly desirable to have a guide that can control the depth of the drilling operation. One such guide is known that has an L-shaped guide member. The leg of the L is hooked over the back side of the panel joint and provides a reference plane for controlling the depth of the drilled hole. The hole is drilled to within a selected distance of the leg.
While this arrangement is satisfactory for readily accessible applications, it can not be used in hard to reach locations or where the distance form a panel edge to a spot weld is greater than the leg of the L, since the leg must be hooked over the edge of the panel. A need thus exists for a spot weld drill guide that can be used in hard to reach locations and where the spot weld is a substantial distance from an edge of a panel.